Resilient lock for a hand tool

Abstract: A hand tool (10) having a pair of elongated members (12, 14) spring-biased to an open position also includes a resilient lock (68) functioning to secure members (12, 14) in closed position. The lock (68) comprises a button (70) having a resilient head (72) and a shank (74) projecting from head (72) and connected to a resilient cap (78) by a fastener (82). Head (72) and cap (78) have respective concavely-shaped faces (76, 80) which are effectively in contact with tool (10) along annular regions (79, 85).

Description: FIELD OF THE INVENTION This invention relates to tools of the type which are resiliently biased to an open position, and that have a locking mechanism to keep these tools in a closed configuration. BACKGROUND OF THE INVENTION Hand-held garden tools such as pruning shears of the pass-by or anvil-type, wire snips, pliers, and certain other cutting implements such as scissors include a spring mechanism for urging the handles in the "open" position. These implements also usually include a lock mechanism functioning against the action of the spring to maintain the blades in closed position. Conventional locks for hand-held cutters include a pivoting member secured to one of the cutting jaws, pivotable into abutting relationship with the opposing jaw. Other devices employ a pivoting ratchet mechanism which can be moved from a locked to an unlocked position by the user's thumb. Examples of such locks for pruning implements are described in U.S. Patents No. 4,156,311, issued on May 29, 1979 to Wallace, et al.; No. 4,268,963, issued on May 26, 1981 to Harrison; and No. 4,341,016, issued July 27, 1982 to Harrison, et al. As more particularly disclosed in these patents, the locking mechanism comprises a pin slidably positioned in a slot formed in one of the pivoted members to engage a recess or protrusion formed in the other member. Other locking mechanisms comprise a spring biased stationary pin extending into a mating cavity when the tool is in closed configuration. Examples of such locking means are disclosed in U.S. Patents No. 3,357,287 issued on December 12, 1967 to Wertepny, and No. 4,947,553 issued on August 14, 1990 to Bendickson et al. These conventional latching mechanisms have various limitations. For example, certain locking mechanisms of the slidable type do not readily retain their positional adjustment. The slidable pin tends to slide away from its selected position during normal operation of the implement and may impair normal operation of the tool. Other conventional mechanisms which are more reliable are of rather complex construction necessitating several parts, thereby increasing the cost of the tool, and possibly rendering these tools less durable. Thus, it is desirable to provide an inexpensive lock mechanism for items such as pruning shears or the like which can alleviate the problems associated with conventional latch mechanisms, i.e., which has improved positional retention properties, and which requires only a limited number of components of simple configuration to facilitate manufacturing and assembly. SUMMARY OF THE INVENTION An inexpensive lock mechanism according to the invention, for tools having a pair of handles connected to a pair of jaws or other working pieces cooperatively connected to each other for scissor movement and biased in the open position, includes a resilient lock comprising a button compressively joined to a cap. Both the button and cap are made of yieldable material thereby permitting certain flexing of the button and cap to prevent undesirable sliding of the lock out of its selected position during normal operation of the tool. This new lock simplifies manufacturing and assembly of the tool and reduces cost without sacrificing quality. According to another aspect of the invention, in a pivoted tool having a pair of elongated members, the pivot member includes a self-compensating resilient assembly comprising a resilient button compressively joined to a resilient cap. According to a preferred embodiment of the invention, in a pruning shear having two cooperating elongated members, a resilient lock mechanism comprises a resilient cap releasably secured to a resilient button by a fastener. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a side elevation view of a pruning shear having a lock in accordance with the invention, the shear being shown in closed position; Figure 2 is a side elevation view of the pruning shear of Figure 1, shown in the open position; Figure 3 is a cross-sectional view taken along line 3-3 shown in Figure 1; and Figure 4 is an exploded view of the components of the pruning shear shown in Figure 1. DETAILED DESCRIPTION Referring to the Figures, a pruning shear or tool 10 of the invention, having a force applying end 10A and an opposed working end 10B, includes an upper elongated member 12 and a lower elongated member 14, pivotally joined by a pivot bolt 16. Members 12 and 14 are covered by the usual rubber or plastic covering members 18 and 20, respectively. Referring more particularly to Fig. 4, upper member 12 is channel-shaped, and a web 22 connects respective side panels 24 and 26. Web 22 is generally flat, and includes a substantially straightforward edge 23 disposed proximate pivot bolt 16. Side panels 24 and 26 terminate proximate pivot bolt 16 by opposite cheeks 28 and 30, respectively. Lower member 14 is extendable between cheeks 28 and 30. Cheeks 28 and 30 are also disposed on opposite sides of a lower hook or anvil blade 32 and an adjacent confronting upper cutting blade 34 of lower member 14. As shown in Fig. 4, upper blade 34 and lower member 14 are preferably unitary. Lower hook 32 is in pivotal relationship with upper blade 34 by pivot bolt 16, which is extendable transversely through cheeks 28 and 30 and through aperture 36 of lower hook 32. Pivot bolt 16 also extends through aperture 38 of upper blade 34. Pivot bolt 16 is secured by pivot nut 40. Pivot bolt 16, extended through suitably aligned apertures 42 of cheeks 28 and 30, and apertures 36 and 38 defines a fulcrum on which members 12 and 14 are pivoted. A lower blade bushing 44 is extendable through aligned aperture 46 of cheek 30 (not shown), spacing collar 50, aperture 48 of lower blade 32, aligned aperture 46 in cheek 28, and lower blade screw 52. Collar 50 is sleeved on bushing 44 between lower blade 32 and cheek 30, distantly thereof to allow a space for the vertical movement of upper blade 34 relative to lower blade 32. Collar 50 also serves as a stop for the open position of the tool, the curvilinear lower face 54 of upper elongated member 14 coming to bear on collar 50. Relative pivotal movement between upper blade 34 unitary with member 14, and lower blade 32 secured to member 12, is allowed by pivot bolt 16, so that the blades are actuated by convergence or divergence of members 12 and 14. A spring actuated biasing means, preset so as to bias blades 32, 34 to open position, is in the form of a leaf spring 56 concealed within upper member 12 and secured at its outer extremity to the inwardly facing surface of web 22 by a leaf spring rivet 58. Leaf spring 56 is ribbed intermediate its extremities at rib 60 to increase the biasing force applied to the cutting blades. Leaf spring 56 rides along a flat 62 on the upper spine of member 14. As member 14 is brought upwardly relative to member 12 by the pressure of the operator's hand, terminal portion 64 of leaf spring 56 is caused to ride along flat 62. In accordance with the invention and as shown in Figs. 3 and 4, a resilient lock 68 comprises a button 70 having a resilient head 72 and a shank 74 projecting from head 72. Head 72, which is advantageously circular, has a concavely-shaped (i.e., dish-shaped) face 76. Thus, face 76 is effectively in contact with cheek 28 at the periphery of head 72, along an annular region 79 of face 76, as shown in Fig. 3. This permits a certain degree of flexing of head 72 when suitable compressive force is applied to button 70 along its longitudinal axis (i.e., along an axis drawn horizontally in Fig. 3). As a result, the area of annular region 79, which increases or decreases with such compressive force, determines the degree of frictional engagement of face 76 with cheek 28. Head 72 also has a central driver-engageable recess 77 extending inwardly from the outer surface of head 72. Recess 77 is formed for engagement by a driver tool such as an "Allen" driver. The configuration of recess 77 greatly facilitates and renders safer the assembling of lock 68 in tool 10 as production personnel is no longer required to hold button 70 in place while driving it. Resilient lock 68 also comprises a resilient cap 78, preferably configured like head 72, i.e., dish-shaped, having a generally concavely shaped face 80 adjacent cheek 30. Cap 78 is releasably connected to button 70 by fastener 82 engaging a bore 83 of button 70. A centering recess 84 is formed in face 80 to matingly receive the free end of shank 74, thereby facilitating assembling and operation of lock 68 as cap 78 remains centered with button 70. As with button 70, face 80 is effectively in contact with cheek 30 at the periphery of cap 78 along an annular region 85 of face 80, as shown in Fig. 3. This construction permits a certain degree of flexing of cap 78 when compressive force is applied to cap 78 along its axis of symmetry (i.e., along an axis drawn horizontally in Fig. 3). As a result, the area of annular region 85, which increases or decreases with such compressive force (adjustable in a simple and inexpensive manner by fastener 82), determines the degree of frictional engagement of face 80 with cheek 30. Thus, the areas of annular regions 79 and 85 cooperate to provide controlled positional retention of lock 68. Resilient lock 68 permits limited flexing of head 72 and cap 78 in response to rotational adjustment of fastener 82. Such continuous adjustment of frictional engagement of concavely shaped faces 76 and 80 with cheeks 28 and 30, i.e., of the areas of annular regions 79 and 85, respectively, improves, in a relatively inexpensive manner, positional retention of lock 68 during normal operation of tool 10. As shown in Fig. 4, to permit locking or unlocking of tool 10, member 12 is provided with an elongated slot 86, formed in spaced relationship to aperture 42 through member 12, and extending in a direction generally parallel web 22 (i.e., in a direction parallel to the longitudinal axis of tool 10). In addition, member 14 has a generally L-shaped slot 88 formed, in spaced relationship to aperture 38, through member 14. As shown in Fig. 3, when tool 10 is in the closed position, elongated slot 86 and the lower portion of L-shaped slot 88 are substantially in registration. Thus, in closed configuration, lock 68 can be slid toward rear terminus 90 of slot 86 and rear terminus 92 of slot 88 to maintain tool 10 closed against the biasing force of spring 56. Conversely, to unlock tool 10, lock 68 is moved toward front terminus (not identified) of slots 86, 88, thereby allowing lower member 14 to pivot around pivot 16 into the open position. In both instances, due to the resilient construction of lock 68, desired positional location of lock 68 is effectively maintained. In addition to improving positional retention without requiring numerous parts, lock 68 also presents other advantages. In particular and significantly, the substantially identical configuration of head 72 and cap 78 permits ambidextrous operation of tool 10. In addition, head 72 and cap 78 being advantageously circular, the assembly of lock 68 in tool 10 does not necessitate rotational orientation of button 72 or cap 78 with respect to cheeks 28 and 30. Moreover, lock 68 which is preferably made of a self-lubricating resilient material such as nylon 66, is relatively inexpensive to manufacture. In accordance with a second exemplary embodiment of the present invention, and as readily apparent to those skilled in the art, the design of lock 68 could also be used for the pivot of the tool. In particular, pivot bolt 16 can be constructed using resilient lock 68 consisting of a resilient button 70 and a cap 78 releasably connected thereto by a fastener 82. Using the design of lock 68 for the pivot of the tool thereby permits self-compensation of wear in the pivot developed by repeated operation of tool 10. It is understood that the above description is of preferred exemplary embodiments of the present invention and that the invention is not limited to the specific forms described herein. For example, tools having this novel resilient lock mechanism may have a pair of elongated members configured differently from those described herein. These members may also be hingedly connected as opposed to forming a pivot as described in the preferred embodiments. Moreover this invention, which is based on tools having a resilient lock mechanism or a resilient pivot wherein the lock or pivot is comprised of a resilient button compressively joined to a resilient cap, can be carried out in other manners. For example, head 72 and cap 78 need not be of identical configuration or need not have recesses or apertures as disclosed herein. Conversely, button 70 could include only head 72, compressively joined to cap 78 by means other than those described in the preferred embodiments. These and other modifications may be made in the design and arrangement of the elements disclosed herein.

Claims: A hand tool (10) comprising: first and second working pieces (32, 34) disposed for cooperative engagement about a pivot point (16); first and second members (12, 14) secured to a respective one of the working pieces (32, 34) and resiliently biased to an open position, the members (12, 14) having respective first and second slots (86, 88) formed therethrough and being substantially in registration when the working pieces (32, 34) are in closed position; and a resilient lock (68) slidable within the slots (86, 88) for securing the working pieces (32, 34) in the closed position; characterized in that the lock (68) includes a button (70) having a yieldable head (72) merging into a shank (74) extending through the slots (86, 88), the lock (68) further including a cap (78) joined to the button (70) by the shank (74), and in that the head (72) and the cap (78) each have a face (76, 80) concavely shaped so that the head (72) and the cap (78) are effectively in contact with the tool (10) in a respective annular region (79, 85) of each of the faces (76, 80), and further in that the area of the regions is proportional to the degree of compressive force applied to the lock (68), thereby determining the degree of frictional, locking, engagement of the faces (76, 80) with the tool (10). The tool of claim 1 further characterized in that the shank (74) has a bore (83), and the lock (68) further comprises a fastener (82) engaging the bore (83) to permit adjustment of the degree of frictional, locking, engagement of the faces (76, 80) with the tool (10). The tool of claim 1 further characterized in that the head (72) comprises a central driver-engageable recess (77) suitably formed for engagement by a driver tool. The tool of claim 1 further characterized in that the face (80) of the cap (78) has a centering recess (84) matingly engaging the free end of the shank (74). The tool of claim 1 further characterized in that the head (72) of the button (70) and the cap (78) are substantially identically shaped thereby rendering the lock (68) ambidextrous. The tool of claim 1 further characterized in that the head (72) and the cap (78) are substantially circular thereby rendering the lock (68) non-directional. The tool of claim 1 further characterized in that the button (70) and the cap (78) are made out of nylon. The tool of claim 2 further characterized in that the pivot point (16) has the same design as lock (68) and is comprised of a button (70), a cap (78), and a fastener (82). The tool of claim 1 wherein the first slot (86) is an elongated slot formed in spaced relationship to the pivot (16) and substantially parallel to the longitudinal axis of the tool (10), and the second slot (88) is substantially L-shaped, the lower portion of the L-shaped slot (88) being substantially parallel to the axis when the tool (10) is in closed position. A resilient lock (68) for securing together a pair of cooperatively-engaging pivoted elongated members (12, 14) having outer surfaces (28, 30), the lock (68) characterized in that it comprises: (a) a resilient button (70) having a head (72), disposed adjacent the outer surface (28) of one of the members (12), and a shank (74) projecting from the head (72) and extending through a pair of lock-receiving slots (86, 88) formed in a respective one of the members (12, 14) in spaced relationship to the pivotal area, the shank (74) further including a bore (83), the head (72) having a face (76), the face (76) being concavely shaped so that the head (72) is effectively in contact with the outer surface (28) in an annular region (79) of the face (76); and (b) a yieldable cap (78) having a concavely shaped face (80) so that the cap (78) is effectively in contact with the outer surface (30) of the other of the members (14) in an annular region (85) of the cap face (80), the cap (78) being compressively joined to the button (70) by a fastener (82) engaging the bore (83) to permit adjustment of the compressive force applied to the lock (68) and thereby determine the degree of frictional, locking, engagement of the faces (76, 80) with the outer surfaces (28, 30).

Inventors: AUSTIN JERROLD N, LABARRE ERNEST D, AUSTIN, JERROLD N., LABARRE, ERNEST D.
Applicants: FISKARS INC, FISKARS INC.
Application year: 1994
Main classification: A01G3
IPC codes: B25B7, A01G3